CHAPTER 20 - Polymer composite bearings with engineered tribo-surfaces

Abstract

Abstract This chapter presents the details of fabrication of surface-tailored composites based on commingled yarns of carbon and polyether-ether-ketone (PEEK), which is a novel method to eliminate some existing limitations in manufacturing bi-directionally reinforced composites. It further elaborates the need for surface tailoring of tribo-composites with solid lubricants rather than their inclusion in the bulk. The details of the process with various powdery lubricants, such as polytetrafluoroethylene (PTFE), MoS2, graphite, etc., are discussed and influence of these on mechanical properties is presented. Based on these studies, PTFE is proved as most promising lubricant for surface tailoring only on the top surface. PTFE in various forms, such as wool, short fibers of various lengths, long fibers, etc., was used to investigate benefits endowed by surface tailoring. Since the maximum performance enhancement (both mechanical and tribological) was observed due to the long PTFE fibers, bearing was fabricated by proper placement of PTFE fibers in commingled yarn composites of PEEK and carbon fibers (CF). Two bearings with and without surface modification were evaluated under different operating parameters. It was observed that CF at an angle of 45° led to the best combination of friction and wear performance. PTFE fiber inclusion removed the stick-slip problem associated with PEEK apart from reducing coefficient of friction from 0.6 to 0.12 and enhancing wear resistance approximately by 70 times. The bearing thus proved very effective for dry situations with very good combination of friction, wear and mechanical properties.